/* this function encrypts a message*/
void EncryptMessage(HC128_State state, Byte[] message, Byte[] ciphertext, UInt64 msglength)
{
UInt64 i;
UInt32 j;
int messageIndex = 0, ciphertextIndex = 0;
/*encrypt a message, each time 4 bytes are encrypted*/
for (i = 0; (i + 4) <= msglength; i += 4, messageIndex += 4, ciphertextIndex += 4)
{
/*generate 32-bit keystream and store it in state.keystreamword*/
OneStep(state);
{
/*encrypt 32 bits of the message*/
Byte[] ciphertextBytes = ConvertUtil.ConvertUInt32ToBytes(BitConverter.ToUInt32(message, messageIndex) ^ state.keystreamword);
for (int byteIndex = 0; byteIndex < 4; byteIndex++)
{
ciphertext[ciphertextIndex + byteIndex] = ciphertextBytes[byteIndex];
}
}
}
/*encrypt the last message block if the message length is not multiple of 4 bytes*/
if ((msglength & 3) != 0)
{
OneStep(state);
for (j = 0; j < (msglength & 3); j++)
{
ciphertext[j] = (byte)(message[j] ^ BitConverter.GetBytes(state.counter1024)[j]);
}
}
}